There are known in the prior art various forms of protective helmet for use by military personnel such as infantrymen to protect the head of the wearer against injury from missiles and shrapnel. All of these helmets of the prior art incorporate some form of suspension system for supporting the helmet in position on the wearer's head. Most of the headband suspensions are secured to the rigid helmet body by the use of metal fasteners such as screws, for example. One type of such a helmet and suspension assembly is shown in Frieder et al U.S. Pat. No. 2,739,309. These helmet and suspension assemblies of the prior art incorporate a number of more or less serious defects. First, the metal fasteners which are used to secure the suspension to the helmet shell often act as secondary missiles when struck by a piece of flying shrapnel or the like. As a result, the wearer may suffer a more serious injury than that which would occur from the shrapnel. Secondly, suspension systems of the prior art permit "bottoming" of the hard outer shell on the wearer's head under the force of an impact on the outer shell, with the attendant danger of injury to the wearer.
In addition to the defects pointed out hereinabove, the protective helmet assemblies of the prior art suffer from a number of disadvantages. Generally adjustment of the size of the suspension is difficult to accomplish. Most of the suspensions of the prior art accommodate only a very small range of head sizes. The helmets of the prior art are heavy. Suspensions of the prior art are permanently attached to the rigid shell with the result that the parts thereof are difficult to clean.
There have recently been developed a class of materials including aromatic polyimide resins which have been found to have superior ballistic properties. Attempts in the prior art to develop a ballistic helmet incorporating such materials have been unsuccessful in that mass production at relatively low cost has not been feasible.
We have invented an improved protective helmet which overcomes the disadvantages of helmets of the prior art. Our helmet minimizes the danger of injury from fasteners acting as secondary missiles. It prevents bottoming of the hard shell on the wearer's head. Our helmet accomodates a wide range of head sizes. The suspension system of our helmet is readily removable from the rigid shell. Our helmet is lightweight. It permits of the mass production at relatively low cost of a helmet having ballistic properties.